Ejection of DNA molecules from carbon nanotubes

Ejection of DNA molecule from carbon nanotubes subjected to torsion is investigated with molecular dynamics simulations. The wall of a carbon nanotube undergoes a collapse and a corresponding propagation of the collapse when a torsion loading applied to the tube is beyond a critical value. The van der Waals force between the encapsulated DNA molecule and the collapsed wall of the nanotube on one hand is a driving force to push the molecule out of the tube, while may also prevent the ejection when the onset of the collapsed wall is in front of the molecule. To ensure a complete DNA ejection, a design of a stopper, a small fixed portion on the carbon nanotube to prevent the collapsed wall from propagating in front of the DNA molecule, is developed. The effects of the environmental temperature, the torsion loading, and the size of the nanotube on the delivering process of the DNA molecule are also examined. Simulation results demonstrate the feasibility of ejection of DNA molecules from carbon nanotubes subjected to torsion and provide guidance on designs of the DNA delivery in biology and medical applications.